This invention relates to the recovery of hydrocarbons from hydrocarbon-containing plants by enzymatic degradation of cellulosic materials, particularly laticifer cells found in latex-containing plants. Laticifers are plant cells which contain latex.
Considerable effort has been directed toward the development of renewable energy resources to alleviate dependence on fossil fuel. Attention has been focused on the direct production of hydrocarbons from plants wherein biosynthesis of terpenes and related compounds occur. Representative of the terpenes, hydrocarbons of various degrees of polymerization, are the lower terpenes as essential oils, and the higher terpenes, as carotenoids, saponins, and rubber. These materials are held within plant cells composed of cellulose, hemicellulose, pectins, and other materials. The various rubber plants yield their rubber product as a latex which contains various substances in solution and in colloidal suspension. Of the approximately 1,800 species of plants reported to contain rubber, only a few yield enough rubber to make them commercially useful. For example, in Hevea, rubber may constitute 40 to 50% of the latex.
Many early efforts to recover the hydrocarbons contained in plants were geared to such activities as tapping of rubber trees, distillation of pine stumps to obtain hydrocarbon resins, or as byproduct recovery from such activities as sulfate pulping. The crushing of oil seeds to obtain vegetable oils is well-known. Crushing combined with water extraction as well as catalytic processes are known. For example, U.S. Pat. No. 1,740,079 teaches the extraction of rubber from plants such as guayule. The guayule plants are reaped and dried, then crushed by rolls or other suitable machinery so as to open up the pith seams and break the bark. The crushed plants are cut into short pieces and soaked in water until the bark and pith are soft. The entire mass of material is then introduced into a water-filled ball mill and subjected to the action of such mill until the bark and pithy material are separated from the hard woody material. The bark and pithy material are reduced to a pulp. The rubber particles are freed from the rest of the material and are agglomerated to rise to the surface of the water for removal. Another extraction process for recovering hydrocarbon values from whole-plant feedstock crops employs rolling mills that shear and compress plant material between dissynchronous rollers. The action of the rollers ruptures cellular material to facilitate downstream extraction with solvents in contrast to the conventional process in use which is wet milling (Chemical Engineering, Sept. 11, 1978, p. 101). Catalytic processes also have been developed. Hydrolyzed wood chips are converted directly to an oil by means of a sodium carbonate catalyst. (Chemical and Eng. News, Oct. 1, 1979, p. 35). Methods have been suggested to recover certain useful hydrocarbons from plant crops such as solvent extraction of organic materials (Science, 198, Dec. 2, 1977, 942-944), pyrolysis of tree bark to obtain benzene compounds (Tr. Sib. Tekhnol. Inst., 1979, No. 43, 30-33; CA77:90240v), and hydrolysis of carbohydrates in plant biomass to sugars for further processing (Chemical and Eng. News, Apr. 3, 1978, p. 31).
In recent years, cellulose degradation through enzymatic means has been a subject of investigation by various workers. U.S. Pat. No. 3,616,222 teaches use of mixed cultures of enzymes in a process for saccharification of cellulose to increase the rate of converting cellulose to sugar. U.S. Pat. No. 3,812,012 to Buschmann, et al., teaches a method for degrading natural plant material with an enzyme preparation containing pectic acid trans-eliminase as the effective ingredient. Buschmann '012 teaches that while it is known to add pectin hydrolases to digestive preparations to degrade plant material, pectin hydrolases can be very active against soluble pectins but can be less active on genuine plant materials which are chemically and physically linked with other polysaccharide components and therefore differ from the isolated soluble pectins in biochemical properties. U.S. Pat. No. 3,972,775 teaches a process for the conversion of cellulosic materials to sugar in the presence of cellulase enzymes wherein a portion of the cellulase enzyme is recovered for reuse and some of the makeup enzyme is produced in a two-stage operation. U.S. Pat. No. 3,990,944 teaches manufacture of alcohol from cellulosic materials by a one-step process involving the simultaneous reaction of a cellulosic material, a cellulase and an alcohol-producing microorganism. U.S. Pat. No. 3,990,945 teaches a process for enzymatic hydrolysis of cellulose to obtain water-soluble sugars wherein the enzyme source is an aqueous culture mass from which the enzyme is not separated, thereby increasing hydrolysis rates and yields of water-soluble sugars. U.S. Pat. No. 4,009,075 teaches a process for making alcohol from sterilized cellulosic material using cellulase enzyme and yeast. Sterilization eliminates unwanted bacterial strains and aids reaction speeds by causing a partial breakdown of cellulosic fibers. U.S. Pat. No. 4,089,745 teaches a process for enzymatically converting cellulose from corn hulls to glucose. Alkali is used to first liberate cellulose from the corn hulls. U.S. Pat. No. 4,094,742 teaches production of ethanol from cellulose through the combined growth of thermophilic cellulytic sparocytophaga and an ethanol-producing thermophilic bacillus. An alkali or acid treatment degrades lignin sufficiently to make the cellulose available for contact with the mixed culture. U.S. Pat. No. 4,097,333 teaches increased production of glucose from ethylene-treated cellulose. Yields are low without ethylene treatment because of the stranded and crystalline nature of cellulose.
Accordingly, the prior art teaches a number of processes for production of glucose from cellulose in the presence of lignin. Crushing and extraction processes for hydrocarbon-containing plants have also been taught. However, prior art processes have not dealt with the problem of obtaining hydrocarbons from hydrocarbon-containing plants wherein the hydrocarbon content is low and is contained in laticifer cells.
An object of this invention accordingly is to provide a process for production and recovery of hydrocarbons from hydrocarbon-containing plants which permits the effective utilization of whole plant biomass as a raw material source. Another object of this invention is to provide a process for production of liquid hydrocarbons in quantity from plant biomass. Another object of this invention is to provide a process for degradation of cellulose to provide glucose and to break the cellulosic walls of latex-containing cells, thereby releasing hydrocarbon-containing latex and increasing hydrocarbon yields. Another object is to provide increased production of hydrocarbons from renewable natural resources.
These and other objects and advantages will become clear from the following specification.